In flight, a pilot navigates his aircraft according to a flight plan that is filed with the air traffic control (“ATC”) authorities. The flight plan may be manually or electronically loaded into the aircraft's Flight Management System (“FMS”) prior to departure. The flight plan may require that ascent maneuvers, descent maneuvers and turn maneuvers to be conducted at certain waypoints along the planned flight path. Changes to a flight plan and the actual maneuvers that execute the flight plan are positively controlled by ATC authorities and monitored by ATC radar. The ATC radar usually tracks each aircraft during its flight when the aircraft is within radar range.
However, in transoceanic flight, positive ATC is not effective or even possible because the ATC radar does not reach the aircraft at all points along the flight plan. As such, aircraft travel oceanic airspace by following certain aircraft separation procedures using satellite information received from the Automatic Dependent Surveillance-Broadcast (ADS-B) system. However, the separation procedures limit the ability to make altitude changes during flight due to the wide clearance requirements, hindering efficient aircraft operation.
Typically, an ADS-B-equipped aircraft determines its own position using a global navigation satellite system and periodically broadcasts this position and other relevant information to potential ground stations and other aircraft with ADS-B receiving equipment. ADS-B can be used over several different data link technologies, including Mode-S Extended Squitter (1090 ES) operating at 1090 MHz, Universal Access Transceiver (978 MHz UAT), and VHF data link (VDL Mode 4). ADS-B provides accurate information and frequent updates to airspace users and controllers, and hence supports improved use of airspace, reduced ceiling/visibility restrictions, improved surface surveillance, and enhanced safety, for example through conflict management. Under ADS-B, a vehicle periodically broadcasts its own state vector and other information without knowing what other vehicles or entities might be receiving it, and without expectation of an acknowledgment or reply. ADS-B is automatic in the sense that no pilot or controller action is required for the information to be issued. It is dependent surveillance in the sense that the surveillance-type information so obtained depends on the suitable navigation and broadcast capability in the source vehicle
To ease the limitations restricting altitude and other flight plan changes during flight, in trail procedures (“ITP”) have been developed to facilitate flight plan changes while preserving adequate safety separations from other aircraft. This allows aircraft to reach their most efficient cruising altitudes more quickly by permitting smaller clearance requirements. The ITP are more fully described in RTCA DO-312 entitled “Safety, Performance and Interoperability Requirements Document for the In-Trail Procedure in Oceanic Airspace (ATSA-ITP) Application”, RTCA Incorporated, Washington D.C. (2008) and is herein incorporated by reference its entirety in the interest of brevity.
In short, the ITP insures that a minimum distance (“ITP Distance”) is maintained from a reference aircraft while a maneuvering aircraft transitions to a new flight level. The ITP Distance is defined as the distance from a “reference aircraft” or a “potentially blocking aircraft” and an “own ship aircraft” or an “ITP aircraft.” The ITP distance is calculated by taking the difference in distance to a common point along each aircraft's ground track. For aircraft on the same track, this is merely the distance between aircraft. For aircraft on parallel tracks this is the distance between the trailing aircraft and a point abeam of the ITP aircraft and on the track of the trailing aircraft. Under the ITP, the term “crossing traffic” refers to a potentially blocking aircraft that may prevent (i.e., block) an own ship aircraft from performing a specific flight level change because of the proximity of an intersection point. An intersection point is defined by the intersection of a ground track of a crossing aircraft and a ground track of the own ship aircraft.
To help an air crew monitor and comply with the ITP, vertical ITP video displays have been designed to operate with ADS-B and display intersection points and collision points related to the crossing traffic. A collision point is an intersection point. However, ITP vertical displays are not capable of displaying some crossing aircraft icons associated with the intersection points.
Because, ITP vertical displays are not capable of displaying some crossing aircraft icons, vertical ITP displays can render ambiguous, if not misleading, visual information concerning aircraft that are indicated as “crossing traffic” in the plan display. The misleading visual information causes confusion and may be purposefully hidden from display to avoid the confusion.
The potential confusion results from the inability of the vertical ITP display to render a blocking aircraft icon for an aircraft that is not located within 45° of the own ship aircraft's track because such an aircraft is disregarded by the ITP. The vertical ITP display instead renders the potentially blocking aircraft icon at the position where its ground track intersects with the ground tack of the ITP aircraft. In effect, the vertical ITP display may produce a false blocking aircraft icon directly ahead of the ITP aircraft at the ITP distance of the blocking aircraft. A visual check by a pilot will fail to see this air contact, thereby causing confusion.
To supplement the ITP vertical displays, separate plan displays are used in conjunction with the vertical displays to provide amplifying traffic collision avoidance system (TCAS) information corresponding to the information being displayed on the ITP vertical display. However, a TCAS by itself cannot display a ground track intersection that is not a collision point. Hence, both displays have deficiencies concerning the accurate display of crossing traffic under the ITP.
Accordingly, it is desirable to provide an improved ITP display that disambiguates visual information depicting crossing traffic in the ITP context. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.